1. Field of the Invention
The present invention relates in general to the field of information handling system power sources, and more particularly to a system and method for powering an information handling system through a display cable.
2. Description of the Related Art
As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
Today's mobile society has shown a preference for portable information handling systems due to the convenience of such systems in use. A typical portable information handling system has an integrated display, integrated I/O devices and an internal power source that together make the system operable for normal use without any cables tied to fixed resources, such as external AC power sockets or peripheral display and I/O devices. Although not required for operation, some external devices improve the usability of portable information handling systems when used at a fixed location. One example is a cradle that accepts the portable information handling system and provides interfaces for peripheral display and I/O devices. Another example is that users can selectively interface devices to a portable information handling system using ports available at the housing of the portable information handling system. Often, users desire to have a relatively small portable information handling system due to the convenience of smaller size while having a large display available to view images from the portable information handling system. One interface that supports external displays for a portable information handling system is the DisplayPort standard interface. DisplayPort supports bidirectional communication between an information handling system and a display through an auxiliary channel so that setup and use of a display for a portable information handling system is more convenient for an end user.
One difficulty with portable information handling systems is that an internal battery power source has a limited charge to run the system. Often the battery charge expires at inconvenient times, such as when the user has a portable information handling system providing presentation materials through an external projector. The user has to halt the presentation to find and plug in an external power adapter for the information handling system. Industry has made some limited efforts to provide power to and from information handling systems through external interfaces. One example is Power over Ethernet, which provides power through an Ethernet cable that also supports a network interface. DisplayPort includes a power pin (DP_PWR and DP_PWR_RETURN) for the purpose of powering branch devices of the display with power provided from a source device, such as an information handling system. For example, a branch device is a DisplayPort to VGA adapter that makes DisplayPort signals compatible with a VGA display. DP_PWR provides 3.3V with an over current protection threshold of 3 A at the source and 1.5 A at the sink so that total power available is 10 W at the source or 5 W at the sink. However, a DisplayPort compliant cable cannot have wires for DP_PWR so that no direct power path is established between a source and sink. One option used to provide power from a display to an information handling system is the Cinema Display available from Apple's Macbook, which bundles a power cable with a display cable. A similar but now abandoned proprietary connector from Apple combined a DVI, power and USB cable to provide power from an information handling system to a display. Nonstandard bundled cable solutions are not helpful unless an end user has a compatible nonstandard system.